I am trying to use linux kernel doubly linked-list implementation mentioned in https://github.com/torvalds/linux/blob/master/include/linux/list.h in user-space which its user-space implementation can be found in https://gist.github.com/roychen/1710968
following is the code which I used at first and it works fine :)
#include <stdio.h>
#include <stdlib.h>
#include <unistd.h>
#include <string.h>
#include "list.h"
struct Node
{
int data;
char name[10];
struct list_head mylist;
};
int main()
{
LIST_HEAD(plist);
struct Node node1 = {.data = 10, .name = "node1", .mylist = LIST_HEAD_INIT(node1.mylist)};
struct Node node2;
node2.data = 20;
strcpy(node2.name, "node2");
INIT_LIST_HEAD(&node2.mylist);
list_add_tail(&node1.mylist, &plist);
list_add_tail(&node2.mylist, &plist);
struct Node* iter;
list_for_each_entry(iter, &plist, mylist)
{
printf("name = %s, data = %d\n", iter->name, iter->data);
}
return 0;
}
the output of the above code is
name = node1, data = 10
name = node2, data = 20
which is as expected.
now assume that I want to add node1twice
Scenario number 1:
list_add_tail(&node1.mylist, &plist);
list_add_tail(&node1.mylist, &plist);
output 1:
name = node1, data = 10
name = node1, data = 10
name = node1, data = 10
name = node1, data = 10
name = node1, data = 10
name = node1, data = 10
name = node1, data = 10
name = node1, data = 10
name = node1, data = 10
name = node1, data = 10
name = node1, data = 10
name = node1, data = 10
name = node1, data = 10
name = node1, data = 10
... -> non-stopping loop (to infinity)
Scenario number 2:
list_add_tail(&node1.mylist, &plist);
list_add_tail(&node2.mylist, &plist);
list_add_tail(&node1.mylist, &plist);
output 2:
name = node1, data = 10 (-> just one node is added to the list instead of 3 nodes)
The above outputs show that the list.h implementation has bug, at least in one of its function macros.
I don't know where is the bug which we cannot add a node twice in the linked list.
Any idea?! :|
***** EDIT *****
Scenario 3:
list_add_tail(&node1.mylist, &plist);
list_add_tail(&node2.mylist, &plist);
list_add_tail(&node1.mylist, &plist);
struct Node* iter;
list_for_each_entry_reverse(iter, &plist, mylist)
{
printf("name = %s, data = %d\n", iter->name, iter->data);
}
output 3:
name = node2, data = 20
name = node1, data = 10
name = node2, data = 20
name = node1, data = 10
name = node2, data = 20
name = node1, data = 10
name = node2, data = 20
name = node1, data = 10
name = node2, data = 20
name = node1, data = 10
... -> non-stopping loop (to infinity)
